The inventive concept relates generally to semiconductor memory devices. More particularly, the inventive concept relates to methods of programming multi-level cells in non-volatile memory devices.
Semiconductor memory devices may be classified as volatile or non-volatile according to their operative nature. Volatile memory devices lose stored data in the absence of applied power, while non-volatile memory devices are able to retain stored data under such conditions. Contemporary trends in electronic devices demand lower power consumption and smaller overall device size. In response to these demands, NAND flash memory is a popular choice among other types of non-volatile memory, since NAND flash memory enjoys a relatively small size, high integration density, and low power consumption. This is particularly true for NAND flash memory incorporating multi-level memory cells (MLC) configured to store two or more data bits per memory cell.
However, as the integration density of NAND flash memory arrays including MLC has increased, various coupling effects during program operations begin to adversely influence adjacent MLC. Coupling may be classified as bit-line coupling occurring in a bit-line direction and word line coupling occurring in a word line direction. During conventional programming of MLC, word line coupling presents a greater problem than bit-line coupling.
In general, adverse coupling effects during programming of MLC may be understood in terms of an “aggressor cell” and one or more “victim cells”. The aggressor cell is usually the MLC targeted by the program operation (“the target cell”). In contrast, the victim cells are MLC physically adjacent (or proximate) to the target cell during the program operation.